{
  "id": "nginx/upstream-sent-http-version-not-supported",
  "signature": "upstream sent HTTP/2.0 response while reading response header from upstream, client: 10.0.0.5",
  "signature_zh": "上游返回不支持的HTTP/2.0响应",
  "regex": "upstream sent HTTP/2\\.0 response while reading response header from upstream",
  "domain": "nginx",
  "category": "protocol_error",
  "subcategory": null,
  "root_cause": "Upstream server sent an HTTP/2.0 response to nginx that did not negotiate HTTP/2 via ALPN, causing protocol mismatch and connection failure.",
  "root_cause_type": "generic",
  "root_cause_zh": "上游服务器发送了HTTP/2.0响应，但未通过ALPN协商HTTP/2，导致协议不匹配和连接失败。",
  "versions": [
    {
      "version": "nginx 1.20.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "nginx 1.22.1",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    },
    {
      "version": "nginx 1.25.0",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "",
      "why_fails": "Nginx proxy module does not support HTTP/2 as upstream protocol; setting it will cause configuration error.",
      "fail_rate": 0.9,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "As of nginx 1.25.x, HTTP/2 upstream is not supported in the proxy module; this is a limitation of nginx itself.",
      "fail_rate": 0.95,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "The error will recur on every request; retries do not fix the protocol mismatch.",
      "fail_rate": 0.8,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "Configure upstream to use HTTP/1.1 instead of HTTP/2. For example, in Apache: disable HTTP/2 module; in Node.js: set HTTP/1.1 explicitly.",
      "success_rate": 0.85,
      "how": "Configure upstream to use HTTP/1.1 instead of HTTP/2. For example, in Apache: disable HTTP/2 module; in Node.js: set HTTP/1.1 explicitly.",
      "condition": "",
      "sources": []
    },
    {
      "action": "If upstream must use HTTP/2, place a reverse proxy like HAProxy or Caddy between nginx and the upstream that can downgrade HTTP/2 to HTTP/1.1.",
      "success_rate": 0.6,
      "how": "If upstream must use HTTP/2, place a reverse proxy like HAProxy or Caddy between nginx and the upstream that can downgrade HTTP/2 to HTTP/1.1.",
      "condition": "",
      "sources": []
    },
    {
      "action": "Ensure upstream server correctly negotiates HTTP/2 via TLS ALPN (e.g., for nginx as upstream, use 'listen 443 ssl http2;').",
      "success_rate": 0.7,
      "how": "Ensure upstream server correctly negotiates HTTP/2 via TLS ALPN (e.g., for nginx as upstream, use 'listen 443 ssl http2;').",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [
    "Configure upstream to use HTTP/1.1 instead of HTTP/2. For example, in Apache: disable HTTP/2 module; in Node.js: set HTTP/1.1 explicitly.",
    "If upstream must use HTTP/2, place a reverse proxy like HAProxy or Caddy between nginx and the upstream that can downgrade HTTP/2 to HTTP/1.1.",
    "Ensure upstream server correctly negotiates HTTP/2 via TLS ALPN (e.g., for nginx as upstream, use 'listen 443 ssl http2;')."
  ],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": "https://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_http_version",
  "official_doc_section": null,
  "error_code": null,
  "verification_tier": "ai_generated",
  "confidence": 0.82,
  "fix_success_rate": 0.75,
  "resolvable": "true",
  "first_seen": "2024-05-22",
  "last_confirmed": "2024-06-01",
  "last_updated": "2024-06-01",
  "evidence_count": 1,
  "tags": [],
  "locale": "en",
  "aliases": []
}